The present invention relates to a vehicle driving apparatus for driving four wheels of the vehicle using an engine and an electric motor.
A convention vehicle driving apparatus has been known, for example, from JP-A No. Hei 9-2090 (published in 1997), wherein a driving battery is utilized, and only at a low μ road for which start assistant is necessary, a 12-V alternator and a 12-V battery for ancillaries are combined to operate a motor. Another system is known, for example, from JP-A No. Hei 7-231508 (published in 1995), which discloses a system for driving a motor in combination with a 12-V alternator and a 12-V battery for ancillaries.
However, the conventional system having, as a power source, a 12-V generator and a 12-V battery for ancillaries has a problem that electric energy that can be brought from the 12-V battery (for ancillaries) is small, and the period used for 4WD running is limited. Thus, for the continuous up-hills, in which high power must be supplied for a long period of time, the system fails to exhibit sufficient performance.
It is an object of the present invention to provide a vehicle driving apparatus capable of providing the sufficient driving force.